This invention relates to heating and cooling systems and more particularly to an improved system for the utilization of natural thermal energy sources for heating and cooling structures and the like.
A variety of systems utilizing solar energy as a source of thermal energy have been developed for various purposes and with the increasing emphasis on the conservation of hydrocarbon fuels, solar heating systems are becoming increasingly attractive for use in the space heating of structures. Likewise, cooling systems involving the atmospheric radiation of heat energy for cooling fluids are known, although when utilized for structural cooling, the systems normally are employed with a heat pump which requires additional energy input for operation. Because of the intermittent nature of solar heating and atmospheric radiation to effect heating and cooling, an effective thermal energy storage system is required for the containment of thermal energy as conditions permit.
Most thermal energy storage systems, particularly where solar derived thermal energy is concerned, involve the storage of sensible heat in large tanks of water or in rock bins. However, with such systems, the storage capacity is limited by the volume of the storage system. Extremely large storage capacities are generally not economical.
Attempts to utilize the earth as a storage medium for thermal energy have been made but have proved deficient for several reasons. For example large reservoirs for containing hot water and the like are impractical for most installations due to the high cost of preparing the reservoir.
Likewise, systems involving burying lines in the earth through which a heat exchange fluid is circulated have generally proved to be impractical because of the large number of lines required in order to effect the exchange of a practical quantity of heat energy for use in even a small structure such as a single family residence. Another important deficiency in such systems is the formation of an air film around the buried lines which results from compaction of the earth immediately surrounding the line due to the expansion and contraction of the line as the heat exchanger fluid loses thermal energy to the earth. The air film in effect insulates the line and severely inhibits the efficient exchange of thermal energy. Corrosion of the lines is another serious deficiency in such systems.
The present invention overcomes the foregoing deficiencies in underground thermal energy storage systems and provides a highly efficient and economical system for the storage of thermal energy in heating and cooling systems.